List<Integer> list = new ArrayList<>();
list.add(1);
list.add(2);
list.add(3);
StringBuilder b = new StringBuilder();
list.forEach(b::append);
System.out.println(b);
you can also try:
String s = list.stream().map(e -> e.toString()).reduce("", String::concat);
Explanation: map converts Integer stream to String stream, then its reduced as concatenation of all the elements.
Note: This is normal reduction
which performs in O(n2)
for better performance use a StringBuilder
or mutable reduction
similar to F. Böller's answer.
String s = list.stream().map(Object::toString).collect(Collectors.joining(","));